Seismotectonics and Identification of Potential Seismic Source Zones in Taiwan


Taiwan is an active and complex tectonic region with earthquakes occurring as a response to collision between the Philippine Sea and the Eurasian plates. Furthermore, the northward subduction of the Philippine Sea plate in northern Taiwan and the eastward subduction of the Eurasian plate in southernmost Taiwan are significant seismogenic zones. Significant seismic hazards in Taiwan may either be induced by the plate boundary activities associated with Iithospheric friction in the shallow part of the subduction zones at either end of Taiwan or by the intraplate activities due to plate collision. In the latter category, specially recognized as seismic sources for hazard consideration are the blind thrusts in the Western Foothills and the Coastal Plain. Similar to the 1994 Northridge earthquake, such events could be quite hazardous because the seismic sources are directly under populated unban areas. The subduction zone offshore of northern Taiwan is capable of producing Mw > 7.5 events, but much of the source zone will lie offshore. The southern subduction zone extends under the Hengchun Peninsula, but the seismicity appears to be relatively low. Also to be noted are long-tern seismicity patterns, such as the NW-trending belt of events between Miaoli and Puli is that extends from near the surface to depths greater than 40 km. The Longitudinal Valley faults and the Meishan fault are well known. A better understanding of the potential seismogenic structures such as the Longitudinal Valley fault system and Meishan fault may help us in proposing appropriate long term measures to mitigate seismic hazards.

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